The validity of studies of calmodulin's properties depends on quantifiable measures of purity of the enzyme preparation and the proportion of calcium it contains, and requires the availability of extremely pure reagents, buffer, and solvents. Analytical methods have been developed for quantitation of picogram quantities of calcium in highly purified preparations of calmodulin and in the reagents and solvents needed to make the preparations. Preliminary analyses show that the reagents and solvents needed for making ultra-pure enzyme preparations can be freed to satisfactory levels from such ubiquitous contaminants as calcium using techniques developed in our laboratory.